Research Articles
The First Report of Loma salmonae (Microsporidia) in Cultured Yamame Trout Oncorhynchus masou masou in Japan
2022 Volume 57 Issue 1 Pages 20-25
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2022 Volume 57 Issue 1 Pages 20-25
In 2019, a large number of microsporidian xenomas was confirmed in the gills of yamame trout (landlocked masu salmon), Oncorhynchus masou masou, cultured in Tokyo. The spore size was similar to that of the previously reported Loma salmonae, and the nucleotide sequence of the ribosomal RNA gene (1,839 bp) showed 99.9% similarity with that of L. salmonae from Oncorhynchus spp. in North America. Based on the morphological and molecular analyses, the microsporidian from yamame trout was identified as L. salmonae. During October 2019 to July 2021, four cases of L. salmonae infection in yamame trout were confirmed at three fish farms in Tokyo. Loma salmonae is the causative agent of microsporidial gill disease in salmonids, causing economic losses in salmonid aquaculture in North America and Europe. In Japan, Loma sp. was once reported from O. masou masou in Hokkaido, but it was not identified at the species level. This is the first confirmed report of L. salmonae infections in Japan, and also its new host record from O. masou masou.
